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Illustrated White Cats


This is the world's first 100% 3D printed-in-place hourglass. It has an adjustable aperture inside the bottleneck, allowing you to ensure that balls fall for exactly 30 seconds. The middle piece can be twisted clockwise to decrease flow rate, or counterclockwise to increase it.  


Adjustable Aperture

A set of four compliant arms allows the aperture to vary in diameter from 10 mm to 15 mm. With a quick twist, beads of many sizes can be made to flow for 30 seconds.


Arm proportions ensure the aperture retains a preferred diameter without reversion to the initial state. 

Notable Features

Print In Place 

After a mini-support is removed from the center seam, the upper and lower parts of the aperture move independently from each other. No slicer-generated support required. 

Both halves of the aperture have a parabolic cross-section, so beads flow in either direction without clumping.


Slicer Hacking

Varying slicer settings such as extrusion temperature, layer height, and infill over the course of the print improves surface finish, impact resistance, and mechanical performance. 

Manually writing G-code (the instructions that run a printer) can even allow plastic beads to form on the extruder head, from where they fall into a partially printed hourglass. 

3D Printed Sand

Spheres of 4 mm were printed. Extrusion at high temperature maintained adherence between the bottom of the spheres and the raft below. 

Given that many thousands are spheres required, we recommend, in the interest of sanity, using off-the-shelf beads.



Office workers: mindfulness breaks

Maker spaces: technology demonstration

Venture capitalists: elevator pitches


Parametric Design

The depth of the diamond grid texture ranges from 0.3 mm to 1.1 mm as a function of closeness to the TOMO logo. Diamonds close to the logo subtly blend into the flat surface around it. 


Questions about the build? Licensing inquiries? Suggestions for improvement?

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